MH370, carrying 239 people including six Australians and two New Zealanders, dropped off civilian radar on March 8 en route from Kuala Lumpur to Beijing. Two weeks later Malaysian investigators still believe it was "deliberately diverted" by someone on board.

Prime Minister Tony Abbott says it was too early to be sure if they are from the missing plane.

Mr Abbott gave an update on the search for Flight MH370 before leaving Papua New Guinea on Sunday morning.

They were seen with a naked eye, among them a wooden pallet, within a radius of five kilometres in the southern Indian Ocean, the agency said.

A Royal New Zealand Air Force P3 Orion aircraft with specialist electro-optic observation equipment was diverted to the location, but reported sighting only clumps of seaweed.

The aircraft dropped a marker buoy to track the movement of the material and a merchant ship has been tasked to locate and identify it.

The Royal Australian Air Force, the Royal New Zealand Air Force and two chartered civil aircraft supported Saturday’s search for wreckage.

Since ASMA assumed co-ordination of the search on Monday more than 150 hours of air time has been committed by the air crews to the task.

A total of eight aircraft have been tasked by AMSA's Rescue Co-ordination Centre to assist with Sunday's search.

The United States Navy P8 Poseidon aircraft also departed for the search about 11am.

The search has been split into two areas within the same proximity, covering 59,000 square kilometres.

The Royal Australian Navy's HMAS Success and two merchant ships are also in the search area.

Further attempts will be made today to establish whether the objects sighted are in fact related to the missing flight.

Mr Abbott said four more aircraft - two Chinese and two Japanese planes - would join the Indian Ocean search on Sunday.

Chinese satellite image

Hours earlier China released a grainy March 18 satellite image of an object measuring 22.5 metres by 13 metres, just 120 kilometres from where possible wreckage was detected in the ocean two days earlier, about 2500 kilometres south-west of Perth.

The new Chinese satellite imagery suggests at least one large object, Mr Abbott said on Sunday.

"Yesterday one of our civilian search aircraft got visuals of a number of objects in a fairly small area in the overall Australian search zone," he told reporters.

A wooden pallet was among the items, he said.

"Obviously before we can be too specific about what it might be, we need to recover this material. It's still too early to be definite," he said.

Mr Abbott says there is increasing hope that authorities are on the road to discovering what happened to the ill-fated jet.

ASMA said this information, which was provided to Australia on Saturday, would be taken into account during Sunday's search.

James Cook University marine scientist Rob Beaman said it was "unusual" for there to be marine debris in the southern Indian Ocean as large as the object captured in Chinese satellite imagery.

"The scale is important and until we see it up close we can’t discount that it might be from the crash site," Dr Beaman said.

"Even big freight containers, the biggest ones, are not as long as the object in the images. The scale is pretty significant."

Another ocean expert, Charitha Pattiaratchi from the University of Western Sydney, said the search area was outside normal shipping lanes and distant from circular currents in which waste often accumulates.

He said if the objects sighted were recovered experts could determine how the currents had moved them and where the plane may have crashed into the ocean.

The debris could also have been moved into the search area from currents off South Africa or South America, he said.

NASA to help

NASA will check satellite data and point space-based imaging equipment at the search area to assist with the search for the missingplane, CNN reports.

The Earth-Observing-1 (EO-1) satellite and the ISERV camera on the International Space Station would be able to provide images with a resolution that could be used to identify objects of about 30 metres or larger.